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Vivek
10-02-2004, 09:23 PM
Hi
I have noticed that many need a proper distance sensor for their robot.

And unless one makes his own circuit, he has to depend on the Imported Sharp IR sensors, which are not available in India and are expensive..
Even if one goes for ultrasonics as solution, there are no ready made sensors which make the life of any non-Indian hobbyist very easy.

So here is a plan - to make one OpenSource - and i need people to experiment on their breadboards, coz I dont have access to any electronic components and tools right now for my personal work.

So i am considering to design a simple circuit which would function as the cheaper Sharp IR detector and would give analog output voltage proportional to the measured distance.
(TSOP 3pin devices arent suitable...)

I had made such circuits about 4 years or so ago...and i remember it was a big pain getting them work because the specs of IR photodiodes (or photo transistors available in Indian local markets are not even known the shopkeepers (i mean they dont know the part numbers even. its just an IR-LED or IR-photodiode for them...)

So here is the Block diagram i had used-(and obvious one..)



VCC
.--------. +
| | |
| +---. | IR
| | | - Photodiode
| | V ^
| | - | .--------. .--------.
| | | | || | | | | Analog
| IR Tx | | o----||---| Gain | |Peak | Vout
| | V | || | & |--| |-----------o
| | - | | | |Detector| to ADC
| | | .-. |BandPass| | |
| +---' | | '--------' '--------'
| | | |
| | '-'
'--------' |
|
===
GND


Tentative Block Diagram of the IR Distance Sensor
IR Phototransistor may be used.
(created by Andy┬┤s ASCII-Circuit v1.27.2 Beta www.tech-chat.de)


Anyways...
Before begining the design id like to know-

1. Is the range of about 25cm types useful and acceptable to junta ?
anyways its very hard to get higher ranges unless the wavelengths of the LED and Photodiode is matched (and so known by the partnumber)

2. I dont like to post practically unverified designs on my webpage. In fact i put only the designs which are robust and dont need tuning or messing for beginners...
So i need someone who could test the design out practically and form a team..
An oscilloscope would be surely needed..
is there anyone enthu do develop an open-source design like this ?

If someone finds a design on web which works great (and he has tested it) it would save my time...and please post it for others.

cheers!
Vivek